EP0153199B1 - Rückstellbare Polyethylen-Komposition und Gegenstand - Google Patents

Rückstellbare Polyethylen-Komposition und Gegenstand Download PDF

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Publication number
EP0153199B1
EP0153199B1 EP85301158A EP85301158A EP0153199B1 EP 0153199 B1 EP0153199 B1 EP 0153199B1 EP 85301158 A EP85301158 A EP 85301158A EP 85301158 A EP85301158 A EP 85301158A EP 0153199 B1 EP0153199 B1 EP 0153199B1
Authority
EP
European Patent Office
Prior art keywords
article
polyethylene
molecular weight
recoverable
million
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
Application number
EP85301158A
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English (en)
French (fr)
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EP0153199A3 (en
EP0153199A2 (de
Inventor
Nachum Resenzweig
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Raychem Corp
Original Assignee
Raychem Corp
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Filing date
Publication date
Application filed by Raychem Corp filed Critical Raychem Corp
Priority to AT85301158T priority Critical patent/ATE77296T1/de
Publication of EP0153199A2 publication Critical patent/EP0153199A2/de
Publication of EP0153199A3 publication Critical patent/EP0153199A3/en
Application granted granted Critical
Publication of EP0153199B1 publication Critical patent/EP0153199B1/de
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Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C61/00—Shaping by liberation of internal stresses; Making preforms having internal stresses; Apparatus therefor
    • B29C61/003—Shaping by liberation of internal stresses; Making preforms having internal stresses; Apparatus therefor characterised by the choice of material
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
    • C08L23/00—Compositions of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Compositions of derivatives of such polymers
    • C08L23/02—Compositions of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Compositions of derivatives of such polymers not modified by chemical after-treatment
    • C08L23/04—Homopolymers or copolymers of ethene
    • C08L23/06—Polyethene
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29K—INDEXING SCHEME ASSOCIATED WITH SUBCLASSES B29B, B29C OR B29D, RELATING TO MOULDING MATERIALS OR TO MATERIALS FOR MOULDS, REINFORCEMENTS, FILLERS OR PREFORMED PARTS, e.g. INSERTS
    • B29K2023/00—Use of polyalkenes or derivatives thereof as moulding material
    • B29K2023/04—Polymers of ethylene
    • B29K2023/06—PE, i.e. polyethylene
    • B29K2023/0658—PE, i.e. polyethylene characterised by its molecular weight
    • B29K2023/0683—UHMWPE, i.e. ultra high molecular weight polyethylene

Definitions

  • This invention relates to the field of recoverable polymeric compositions and more particularly relates to the field of recoverable polyethylenes.
  • Ultra-high-molecular-weight polyethylenes are generally considered to have a molecular weight in excess of 3 million.
  • a molecular weight of 3 million or more can be defined according to ASTM D-4020-81, wherein the relative viscosity should be 2.3 or more.
  • the interest in UHMWPE results from their superiority with respect to mechanical and impact properties and abrasion and chemical resistance when compared to conventional polyethylenes.
  • UHMWPE One reference which describes an application of UHMWPE is CA-A-1147133. This discloses a process in which a tube of UHMWPE is warmed, slightly expanded, placed while warm over a roller, and then cooled so that it contracts into close contact with the roller. The tube and roller are used as a support for a conveyor belt. There is no disclosure of cross-linking the UHMWPE.
  • polyethylenes may be imparted with shape memory.
  • Crosslinking either by chemical curing or by radiation, improves the shape memory of the polyethylenes.
  • Work on very high molecular weight polyethylenes has been previously disclosed in GB-A-1,095,772.
  • polyethylenes having a molecular weight in excess 1 million were crosslinked and compared against non-crosslinked polyethylenes of similar molecular weight.
  • Certain mechanical properties of both groups of polyethylenes were measured at temperatures above their respective melting points.
  • Recovery force can be characterized by stress relaxation behaviour as determined by a stress relaxation test. In this test, a sample is stretched at constant strain rate to a particular length and then with the strain rate set at zero, the stress as a function of time is measured.
  • the invention provides a process for the preparation of a heat-recoverable article comprising
  • the invention also provides heat recoverable articles directly obtained by processes according to the present invention, and recovered articles made by recovering such heat recoverable articles.
  • the recoverable articles made by process of the present invention may be a tubular coupling having an inside diameter or a shrink ring having an inside diameter.
  • the crosslinking of the polyethylene may be accomplished by any of the known methods such as by radiation or by chemical curing.
  • the preferred crosslinking method is by radiation.
  • Figure 1 illustrates stress relaxation curves for various polyethylenes ranging in molecular weight from .6 million to 5.0 million.
  • Polyethylene tensile specimens in the unbeamed state were cut cut of a UHMWPE sheet.
  • the tensile specimens were subjected to tensile tests on an Instron with the crosshead speed set at 12.7 cm (5 inches) per minute.
  • the crossheads moved from a separation distance of 3.0 cm (1.2 inches) to 10.7 cm (4.2 inches), so that a 2.5 cm (1 inch) length on the tensile speciman became 8.9 cm (3.5 inches)
  • the strain rate of the Instron was set at zero. Then the stress as a function of time was measured and plotted.
  • the preferable recovery force may be defined more particularly with reference to Figure 4.
  • Figure 4 is similar to Figure 2 except that Figure 4 now includes two straight lines A and B.
  • Lines A and B approximate the preferred ranges of the recovery force over the times of 0.1 to 30 minutes and at a temperature of 120°C
  • Line A actually describes the lower limit of one preferred range of recovery force. Thus it is preferred that at any unit of time and at 120°C., the recovery force should be above line A.
  • the heat source may either be in the form of an intense source such as a torch or in a more general form such as oven heating. In any case, an evenly distributed heat flux which does not over heat the surface is needed in order to assure a high quality product.
  • the process comprises expanding at or below the melting point of the composition. More preferably, the composition should be expanded within the temperature range of room temperature to about 140°C.
  • the melting point of these polyethylenes is actually a melting range which extends from about 130°C - 140°C. 140°C is considered to be the upper end of the temperature range at which the material will be at least partially crystalline. Even more preferably, the composition should be expanded within a temperature range of room temperature to 125°C
  • the composition be recovered within the temperature range of room temperature to 140°C. More preferably, the composition should be recovered within the temperature range of 75°C to 120°C.
  • the composition is preferably recovered at a temperature such that the temperature at recovery is always greater than the temperature at expansion. Also the temperature at recovery is preferably at or less than the melting point of the material When these precepts are adhered to, it is found that the recovery force is at a maximum.
  • composition of the present invention was prepared in the following manner: The resin Hostalen GUR 413, the ultra-high-molecular-weight polyethylene powder, was blended with antioxidants in a high-speed dry blender for about ten minutes. The compound was then loaded into a cylindrical sleeve mold. The compound was compacted in the mold in order to reduce its porosity. The compaction pressure was 100kgf/cm2 at room temperature for about five minutes. The compacted product was sintered under ambient air at 220°C for thirty minutes. The applied pressure during sintering was 50kgf/cm2.
  • the product was cooled in the mold under pressure at 300 kgf/cm2 to about 50°C, at which temperature the mold was opened and the product released.
  • the size of the cylindrical sleeve was two inches in length with a 1.78cm (0.7 inch) inside diameter and a 3.56 cm (1.4 inch) outside diameter.
  • the product was crosslinked by exposing it to a high-energy electron beam. Dosage was in order of 6 megarads.
  • the cylindrical sleeve was then expanded at 80°C by a conical mandrel. After expansion, the inside diameter of the cylindrical sleeve was 6.35 cm (2.5 inches). The expansion ratio was 3.57X. The expansion ratio is the ratio of the inside diameter after expansion to the inside diameter before expansion. Subsequent to the expansion, the cylindrical sleeve was stored until ready for use.
  • a second cylindrical sleeve was made according to Example 1. In this case, however, after it had been expanded, the sleeve was sliced into several rings with each ring having a length of about 0.6 cm (one-quarter inch). These rings would now be used as shrink rings.
  • a rubber sleeve was placed over an electrical connector and then the shrink ring was placed over the rubber sleeve and shrunk at 120°C in an oven. When the shrink ring was shrunk, it provided a water-tight seal so that water was prevented from entering between the rubber sleeve and the electrical connector.
  • a third cylindrical sleeve was made according to Example 1. This sleeve was sliced into sections of about 2.54 cm (1 inch) in length. This 2.54 cm (1 inch) section was then recovered upon a substrate which would then be used as a bearing means.
  • the bearing means would have a bearing surface.
  • the outer periphery of the bearing means represents the bearing surface and the recovered polyethylene forms at least a portion of this bearing surface. It has been found that this bearing means may be used as a rotatable article. Due to the high recovery force of the crosslinked polyethylene of this invention, there is no possibility of slippage between the recovered polyethylene and the substrate.
  • Recoverable articles employing the composition of this invention may be expanded up to about ten times its original inside diameter, although expansion up to eight times its original diameter is much preferred. Modifications may be made within the scope of the claims.

Landscapes

  • Chemical & Material Sciences (AREA)
  • Health & Medical Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Medicinal Chemistry (AREA)
  • Polymers & Plastics (AREA)
  • Organic Chemistry (AREA)
  • Shaping By String And By Release Of Stress In Plastics And The Like (AREA)
  • Compositions Of Macromolecular Compounds (AREA)
  • Graft Or Block Polymers (AREA)
  • Addition Polymer Or Copolymer, Post-Treatments, Or Chemical Modifications (AREA)
  • Treatments Of Macromolecular Shaped Articles (AREA)
  • Materials For Medical Uses (AREA)

Claims (9)

  1. Verfahren zur Herstellung eines wärmerückstellbaren Gegenstands, das folgende Schritte aufweist:
    (i) Vernetzen eines Gegenstands, der aus einer Zusammensetzung besteht, die Polyethylen mit einer relativen Viskosität von 2,3 oder mehr und einem Molekulargewicht von mehr als ca. 3,0 Millionen gemäß der Definition von ASTM D-4020-81 aufweist; und
    (2) Aufweiten des vernetzten Gegenstands.
  2. Verfahren nach Anspruch 1, wobei das Vernetzen durch Bestrahlung erfolgt.
  3. Verfahren nach Anspruch 1 oder 2, das aufweist: Aufweiten des Gegenstands bei einer Temperatur unter dem Schmelzpunkt der Zusammensetzung.
  4. Verfahren nach Anspruch 1, 2 oder 3, das aufweist: Aufweiten des Gegenstands bei einer Temperatur zwischen Raumtemperatur und 140 °C, bevorzugt zwischen Raumtemperatur und 125 °C.
  5. Verfahren nach einem der vorhergehenden Ansprüche, das aufweist: Vernetzen von Polyethylen mit einem Molekulargewicht von 3,0-5,0 Millionen.
  6. Verfahren nach einem der vorhergehenden Ansprüche, das aufweist: Aufweiten des Gegenstands bis zum 8fachen.
  7. Wärmerückgestellter Gegenstand, der hergestellt ist durch Rückstellen eines wärmerückstellbaren Gegenstands, der eine vernetzte Zusammensetzung aufweist, die Polyethylen mit einer relativen Viskosität von 2,3 oder mehr und einem Molekulargewicht von mehr als ca. 3,0 Millionen gemäß der Definition von ASTM D-4020-81 umfaßt.
  8. Gegenstand nach Anspruch 7 in Kombination mit einem Substrat, um das herum der wärmerückstellbare Gegenstand rückgestellt worden ist.
  9. Gegenstand in Kombination mit einem Substrat nach Anspruch 8, wobei das Substrat ein Rohr oder ein Lager ist.
EP85301158A 1984-02-21 1985-02-21 Rückstellbare Polyethylen-Komposition und Gegenstand Expired - Lifetime EP0153199B1 (de)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AT85301158T ATE77296T1 (de) 1984-02-21 1985-02-21 Rueckstellbare polyethylen-komposition und gegenstand.

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US58210584A 1984-02-21 1984-02-21
US582105 1984-02-21

Publications (3)

Publication Number Publication Date
EP0153199A2 EP0153199A2 (de) 1985-08-28
EP0153199A3 EP0153199A3 (en) 1986-11-12
EP0153199B1 true EP0153199B1 (de) 1992-06-17

Family

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Family Applications (1)

Application Number Title Priority Date Filing Date
EP85301158A Expired - Lifetime EP0153199B1 (de) 1984-02-21 1985-02-21 Rückstellbare Polyethylen-Komposition und Gegenstand

Country Status (5)

Country Link
EP (1) EP0153199B1 (de)
JP (1) JPS60210607A (de)
AT (1) ATE77296T1 (de)
CA (1) CA1257745A (de)
DE (1) DE3586209T2 (de)

Families Citing this family (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4872713A (en) * 1987-02-19 1989-10-10 Raychem Corporation Coupling device
AU603020B2 (en) * 1988-12-06 1990-11-01 Asea Brown Boveri Ab Surge arrester
WO1996009330A1 (fr) 1994-09-21 1996-03-28 Bmg Incorporated Piece moulee en polyethylene a poids moleculaire ultra eleve utile pour les articulations artificielles et son procede de fabrication
US7344672B2 (en) 2004-10-07 2008-03-18 Biomet Manufacturing Corp. Solid state deformation processing of crosslinked high molecular weight polymeric materials
US7462318B2 (en) 2004-10-07 2008-12-09 Biomet Manufacturing Corp. Crosslinked polymeric material with enhanced strength and process for manufacturing
US8262976B2 (en) 2004-10-07 2012-09-11 Biomet Manufacturing Corp. Solid state deformation processing of crosslinked high molecular weight polymeric materials
US8641959B2 (en) 2007-07-27 2014-02-04 Biomet Manufacturing, Llc Antioxidant doping of crosslinked polymers to form non-eluting bearing components

Family Cites Families (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB1095772A (en) * 1963-09-17 1967-12-20 Raychem Ltd Crosslinked polymeric compositions
CA1147133A (en) * 1980-08-29 1983-05-31 Denis Thibault Method for manufacturing rollers or idlers

Also Published As

Publication number Publication date
DE3586209D1 (de) 1992-07-23
EP0153199A3 (en) 1986-11-12
EP0153199A2 (de) 1985-08-28
JPS60210607A (ja) 1985-10-23
DE3586209T2 (de) 1993-01-28
CA1257745A (en) 1989-07-18
ATE77296T1 (de) 1992-07-15

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